Joyce Reed, a senior house officer at St James' University Hospital in Leeds and Peter Trigwell, a consultant in liaison psychiatry at Leeds General Infirmary, published their findings in the Psychiatric Bulletin from the Royal College of Psychiatrists.

'Raises concerns'

A test customer at health shops described a range of symptoms, including lethargy, lack of concentration, poor appetite and disturbed sleep.

Five of the shops were visited and five were telephoned, with most of the staff asking extra questions before making recommendations.

But only two asked the customer if they had consulted their GP and staff made no response when the "customer" explained she was taking the oral contraceptive pill, despite evidence St John's Wort can reduce its effectiveness.

One staff member explained she was not medically trained and that it would be wise to see a GP first.

The report said: "This study raises concerns about the virtually complete separation and independence of complementary and alternative medicine services from the National Health Service and pharmaceutical agencies.

"However, owing to the lack of overlap between the two sectors little is understood about each in either area.

"A more integrated approach would allow patients to benefit from herbal preparations, such as St John's Wort, with optimum safety."